Twitter is free, operational, easily accessible and known.

Finding a mastodon instance is a pain today. And "run your own" is not a great option. (It's a pain to run your own publicly accessible anything, these days. I will never go back to running my own email server ever again)

I suppose. I’ve also got 20x the followers on Twitter because I’ve been using it actively for years, but I’ve only recently started using mastodon. I can certainly say I’ve learned more about mastodon from posts on mastodon, but in this instance a user from twitter was helpful. Notably that user is also on mastodon. I’ll have to check to see if we’re following each other there. Every day I find more of my twitter friends on mastodon, and it’s a lovely feeling.